This invention relates generally to doors and windows and more specifically to the jambs of door and window openings that frame the openings and into which doors and windows are mounted.
When constructing the doors and windows of a building, a rough opening is usually formed with framing timbers, which in residential housing are generally 2xc3x974 studs. A prefabricated frame is then installed in the rough opening. In the case of a door, this frame generally comprises a threshold and sill assembly defining the bottom of the frame, a pair of spaced vertical jambs defining the sides of the frame, and a head jamb at the top of the frame. The jambs are formed to receive the door panel, which is mounted to one of the vertical jambs by hinges, and to provide a peripheral stop against which the door rests when it is closed. In many cases, weather stripping is provided along the stop to form a seal between the door panel and the stop in order to prevent unwanted drafts through the closed door.
For many years, door jambs, and window jambs for that matter, have been formed of elongated planks or boards of wood that are milled to form the contour of the jamb and to define the raised peripheral stop of the jamb. Since the surfaces of these jambs are generally visible, it has historically been necessary to fabricate door jambs from high grade clear lumber that has no knots, is stable when subjected to moisture, and can be stained and painted with superior results. Although such lumber was plentiful from old growth forests for decades, it has become increasingly rare and correspondingly expensive over the past several years. As a result, old style door frames made of milled clear lumber are quickly becoming cost prohibitive, and can only continue to follow this trend as old growth forests are progressively harvested.
Some attempts have been made to reduce the reliance on expensive lumber in the fabrication of door and window jambs. For example, vinyl clad jambs fabricated of less expensive lower grade lumber covered by a skin of extruded vinyl have become popular. However, these types of jambs still require the time consuming process of milling the wooden jamb members to the desired contour, extruding a vinyl cladding contoured to fit over the wooden jambs, and installing the cladding on the jambs during the manufacturing process. As a result, some vinyl clad jambs can be even more expensive than all wood jambs formed of high grade lumber.
Another attempt to solve the problem has been to fabricate a combination jamb with interior portions made of high grade lumber but with exterior portions made of vinyl or plastic extrusions. These composite jambs have met with some success but still require the use of some high grade lumber for interior portions of the jambs. Further, most of these types of jambs require specialized installation techniques, which carpenters resist. Finally, as with all jambs that include wood, the wooden portions of the jamb are subject to rot and decay over time, particularly in the region of the door sill,.and require replacing over time.
While a door jamb having no wooden components would seem to be a solution to the problem, this has proven an illusive goal for door and window manufacturers. Hollow extruded plastic jambs, while not including any wood, are flimsy, do not take nails and screws like wood, and are generally unacceptable in all but the most inexpensive construction. Solid extruded plastic jambs have not proven practical because the plastic is not as strong as wood and is subject to much greater thermal expansion and contraction than wood, which can cause the jamb to buckle or deform under extreme temperature conditions.
Accordingly, there exists a need for a novel door and window jamb assembly that uses no wood, that is resistant to rot and decay for much longer periods of time than wood, that is installed using traditional carpentry techniques, and that is not subject to degradation due to thermal expansion and contraction. It is to the provision of such a jamb assembly that the present invention is primarily directed.
Briefly described, the present invention, in one embodiment thereof, comprises an improved door jamb assembly fabricated entirely of coextruded thermoplastic material. The jamb is coextruded with a porous blown thermoplastic core and a solid non blown thermoplastic skin that is adapted to be primed and painted. The jamb is extruded to have the desired profile, and, in the preferred embodiment, has a jamb portion and a raised portion that forms a stop against which a closed door can rest. A groove is extruded along the bottom of the stop for holding a flexible whether strip for sealing against the door.
A pair of rolled or extruded aluminum reinforcing members are coextruded with the jamb and are embedded within the blown core thereof. The reinforcing members are shaped to be surrounded and be gripped by the thermoplastic material of the jamb. The reinforcing members function to minimize the thermal expansion and contraction of the jamb member and to eliminate any tendency of the member to bow or deform when exposed to changes in temperature. In the preferred embodiment, one of the reinforcing members has a leg that is positioned adjacent the inside edge of the jamb for receiving screws or other fasteners that mount a decorative case molding to the jamb. Similarly, the other reinforcing member has a leg that is positioned adjacent the outside edge of the jamb for receiving screws or other fasteners used to attach a brick mold to the jamb. This provides additional reinforcement to the jamb since the reinforcing members are firmly attached to the case molding inside a building and the brick mold on the outside of the building.
Accordingly, an blown all thermoplastic door jamb is now provided that uses no wood, is efficient to manufacture with a minimum of manufacturing steps, that is not subject to rot and decay, and that is strong and thermally stable even under extreme temperature conditions. These and other objects, features, and advantages of the invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawings, which are briefly described as follows.